JP2008175547A - Distance meter and distance measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve distance resolution in a range finder and a distance measuring method for determining the distance to an object to be measured by counting the number of MHPs through the use of a counter. <P>SOLUTION: The range finder comprises: a laser driver 4 for making a semiconductor laser 1 alternately repeat a first oscillation period in which its oscillation wavelength continuously increases and a second oscillation period in which its oscillation wavelength continuously decreases; a photodiode 2 for converting output of the semiconductor laser 1 into electrical signals; a counting device 8 for counting the number of interference waveforms contained in output of the photodiode 2; and an arithmetic unit 9 for computing the distance to the object to be measured 12 on the basis of the number of the interference waveforms. The counting device 8 has a verification means for verifying the number of the interference waveforms to some places of decimals on the basis of an initial value and a final value of waveforms in a counting period for counting the number of the interference waveforms and a result of counting of the interference waveforms. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an interference type distance meter and a distance measurement method for measuring a distance from a measurement object using light interference.

  Distance measurement using light interference by a laser has long been used as a highly accurate measurement method without disturbing the measurement object for non-contact measurement. Recently, a semiconductor laser is being used as a light source for optical measurement in order to reduce the size of the apparatus. A typical example is one using an FM heterodyne interferometer. This is capable of relatively long distance measurement and good accuracy, but has the disadvantage that the optical system becomes complicated because an interferometer is used outside the semiconductor laser.

  On the other hand, a measuring instrument using interference (self-coupling effect) in the semiconductor laser between the laser output light and the return light from the measurement object has been proposed (for example, Non-Patent Document 1, Non-Patent Document). 2, see Non-Patent Document 3). According to such a self-coupled laser measuring instrument, the semiconductor laser with a built-in photodiode serves as the functions of light emission, interference, and light reception, so that the external interference optical system can be greatly simplified. Therefore, the sensor unit is only a semiconductor laser and a lens, and is smaller than the conventional one. In addition, the distance measurement range is wider than the triangulation method.

  FIG. 7 shows a composite resonator model of an FP type (Fabry-Perot type) semiconductor laser. In FIG. 7, 101 is a semiconductor laser, 102 is a wall opening of a semiconductor crystal, 103 is a photodiode, and 104 is an object to be measured. Part of the reflected light from the measurement object 104 easily returns to the oscillation region. The small amount of light that has returned returns to the laser beam in the resonator 101, and the operation becomes unstable, causing noise (composite resonator noise or return light noise). The change in the characteristics of the semiconductor laser due to the return light appears remarkably even if the amount of return light relative to the output light is very small. Such a phenomenon is not limited to a Fabry-Perot type (hereinafter referred to as FP type) semiconductor laser, but also other types such as a vertical cavity surface emitting laser type (hereinafter referred to as a VCSEL type) and a distributed fed back laser type (hereinafter referred to as a DFB laser type). This also appears in the same semiconductor laser.

If the oscillation wavelength of the laser is λ and the distance from the wall open surface 102 closer to the measurement target 104 to the measurement target 104 is L, the return light and the laser light in the resonator 101 are as follows when the following resonance condition is satisfied. Strengthen and slightly increase the laser power.
L = nλ / 2 (1)
In formula (1), n is an integer. This phenomenon can be sufficiently observed even if the scattered light from the measurement object 104 is very weak, because the apparent reflectance in the resonator 101 of the semiconductor laser increases, causing an amplification effect.

  Since the semiconductor laser emits laser beams having different frequencies according to the magnitude of the injection current, an external modulator is not required when modulating the oscillation frequency, and direct modulation is possible by the injection current. FIG. 8 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 103 when the oscillation wavelength of the semiconductor laser is changed at a certain rate. When L = nλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the resonator 101 becomes 0 ° (same phase), and the return light and the resonator 101 When L = nλ / 2 + λ / 4, the phase difference is 180 ° (opposite phase), and the return light and the laser light in the resonator 101 are the weakest. Therefore, when the oscillation wavelength of the semiconductor laser is changed, a place where the laser output becomes strong and a place where the laser output becomes weak appear alternately, and the laser output at this time is detected by the photodiode 103 provided in the resonator 101. As shown in FIG. 8, a step-like waveform having a constant period is obtained. Such a waveform is generally called an interference fringe.

  Each stepped waveform, that is, each interference fringe is called a mode pop pulse (hereinafter referred to as MHP). MHP is a phenomenon different from the mode hopping phenomenon. For example, if the number of MHPs is 10 when the distance to the measurement object 104 is L1, the number of MHPs is 5 at half the distance L2. That is, when the oscillation wavelength of the semiconductor laser is changed for a certain time, the number of MHPs changes in proportion to the measurement distance. Therefore, if the MHP is detected by the photodiode 103 and the frequency of the MHP is measured, the distance can be easily measured.

Tadashi Ueda, Satoshi Yamada, Susumu Shito, “Distance Meter Using Self-Coupling Effect of Semiconductor Laser”, Proceedings of the 1994 Tokai Branch Joint Conference of Electrical Engineering Society, 1994 Satoshi Yamada, Susumu Shito, Norio Tsuda, Tadashi Ueda, “Study on a small rangefinder using the self-coupling effect of a semiconductor laser”, Aichi Institute of Technology research report, No. 31 B, p. 35-42, 1996 Guido Giuliani, Michele Norgia, Silvano Donati and Thierry Bosch, “Laser diode self-mixing technique for sensing applications”, JOURNAL OF OPTICS A: PURE AND APPLIED OPTICS, p. 283-294, 2002

  In a conventional interference type distance meter including a self-coupled type, the number of MHPs is measured using a counter, or the MHP frequency is measured using an FFT (Fast Fourier Transform), so that the distance to the measurement object is measured. I was asking for. In the distance meter using FFT, since the frequency of MHP is measured and replaced with the number of MHPs, the number of MHPs can be measured in decimal units, and the distance to the measurement object can be measured with high resolution. On the other hand, a distance meter using a counter has an advantage that the circuit configuration is simplified. However, since the number of MHPs can be counted only in an integer unit, the distance resolution is lower than when using FFT. There was a problem of becoming.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to improve distance resolution in a distance meter and a distance measurement method for measuring the number of MHPs using a counter and obtaining a distance from a measurement object. And

The distance meter of the present invention includes at least a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously, and a period in which the oscillation wavelength continuously decreases monotonously. A laser driver that operates the semiconductor laser so that second oscillation periods including the second oscillation period alternately exist, and a light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement target into an electrical signal And counting means for counting the number of interference waveforms generated by the laser light emitted from the semiconductor laser and the return light from the measurement object included in the output signal of the light receiver, and a count for counting the number of the interference waveforms Determining means for determining the number of interference waveforms in decimal units from the initial value and final value of the interference waveform in the period and the counting result of the counting means; Therefore in which the number of the determined interference waveform and a calculating means for calculating a distance between the measurement object.
The distance meter of the present invention includes a semiconductor laser that emits laser light to a measurement target, a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously, and a period in which the oscillation wavelength continuously decreases monotonously. Included in the output signal of the laser receiver, the laser driver that operates the semiconductor laser so that the second oscillation period including at least the second oscillation period alternately exists, the optical receiver that converts the optical output of the semiconductor laser into an electrical signal, and Counting means for counting the number of interference waveforms caused by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, and the interference waveform in the counting period for counting the number of interference waveforms. From the initial value and the final value and the counting result of the counting means, a determining means for determining the number of interference waveforms in decimal units, and the interference determined by the determining means From the number of forms and has a calculating means for determining the distance between the measurement object.

Further, in one configuration example of the distance meter of the present invention, the counting unit counts rising edges of the interference waveform, and the determination unit determines whether the initial value of the interference waveform is high and the final value is also high. When the initial value of the interference waveform is low level and the final value is also low level, the counting result of the counting means is determined as the number of interference waveforms, and the initial value of the interference waveform is high level and the final value is low level. In this case, a value obtained by adding 0.5 to the counting result of the counting means is determined as the number of the interference waveforms, and when the initial value of the interference waveform is low level and the final value is high level, A value obtained by subtracting 0.5 from the counting result is determined as the number of the interference waveforms.
Further, in one configuration example of the distance meter of the present invention, the counting unit counts falling edges of the interference waveform, and the determination unit determines that the initial value of the interference waveform is high level and the final value is also high level. Alternatively, when the initial value of the interference waveform is low level and the final value is also low level, the counting result of the counting means is determined as the number of interference waveforms, and the initial value of the interference waveform is high level and the final value is low. In the case of level, a value obtained by subtracting 0.5 from the counting result of the counting means is determined as the number of the interference waveforms, and when the initial value of the interference waveform is low level and the final value is high level, the counting means A value obtained by adding 0.5 to the counting result is determined as the number of the interference waveforms.

Further, the present invention radiates a wavelength-modulated wave to a measurement object, detects interference generated between the wave reflected back to the measurement object and the radiated wave, and measures the measurement based on the number of interference waveforms. In the distance measurement method for determining the distance to the target, the number of the interference waveforms is determined in decimal units from the initial and final values of the interference waveform and the counting result of the interference waveform in the counting period for counting the number of the interference waveforms. And a calculation procedure for obtaining a distance to the measurement object from the number of interference waveforms determined by the determination procedure.
Further, the present invention provides a distance measurement method for emitting laser light to a measurement object using a semiconductor laser, wherein the first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the oscillation wavelength continuously monotonously. An oscillation signal for operating the semiconductor laser so that second oscillation periods including at least a decreasing period alternately exist, and laser light emitted from the semiconductor laser and return light from the measurement object are electric signals. A counting procedure for counting the number of interference waveforms caused by the laser light emitted from the semiconductor laser and the return light from the measurement object, and a count for counting the number of the interference waveforms, included in the output signal of the light receiver to be converted into A determination procedure for determining the number of interference waveforms in decimal units from the initial value and final value of the interference waveform in the period and the counting result of the counting procedure; In which the number of the determined interference waveform by sequentially and a calculation procedure for obtaining the distance to the measurement target.
Further, the present invention provides a distance measurement method for emitting laser light to a measurement object using a semiconductor laser, wherein the first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and the oscillation wavelength continuously monotonously. An oscillation procedure for operating the semiconductor laser so that second oscillation periods including at least a decreasing period alternately exist, and an output signal of a light receiver that converts an optical output of the semiconductor laser into an electrical signal; A counting procedure for counting the number of interference waveforms caused by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, and an initial value of the interference waveform in a counting period for counting the number of interference waveforms And a determination procedure for determining the number of interference waveforms in decimal units from the final value and the counting result of the counting procedure, and an interference wave determined by the determination procedure. In which the number and an algorithm for determining the distance between the measurement object.

  According to the present invention, there is provided interference determining means for determining the number of interference waveforms in units of decimal points from the initial value and final value of the interference waveform in the counting period for counting the number of interference waveforms and the counting result of the counting means. Since the number of waveforms can be counted in decimal units, the distance resolution can be improved in a distance meter that measures the number of interference waveforms using a counting means (counter) to determine the distance to the measurement object.

  The present invention is a method for measuring a distance based on an interference signal between a wave emitted in sensing using wavelength modulation and a wave reflected by an object. Therefore, the present invention can also be applied to an optical interferometer other than the self-coupling type and an interferometer other than light. More specifically, the case where the self-coupling of the semiconductor laser is used will be described. When the laser oscillation wavelength is changed while irradiating the measurement target from the semiconductor laser, the oscillation wavelength changes from the minimum oscillation wavelength to the maximum oscillation wavelength. The displacement of the measurement object during the change (or during the change from the maximum oscillation wavelength to the minimum oscillation wavelength) is reflected in the number of MHPs. Therefore, the state of the measurement object can be detected by examining the number of MHPs when the oscillation wavelength is changed. The above is the basic principle of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a distance meter according to an embodiment of the present invention. 1 includes a semiconductor laser 1 that emits laser light to a measurement target, a photodiode 2 that converts the optical output of the semiconductor laser 1 into an electrical signal, and a light that is collected from the semiconductor laser 1 to be measured. 12, the return light from the measuring object 12 is collected and incident on the semiconductor laser 1, and the first oscillation period in which the oscillation wavelength continuously increases in the semiconductor laser 1 and the oscillation wavelength are continuous. Laser driver 4 that alternately repeats a second oscillation period that decreases gradually, a current-voltage conversion amplifier 5 that converts and amplifies the output current of the photodiode 2 into a voltage, and an output of the current-voltage conversion amplifier 5 A filter circuit 11 that removes a carrier wave from the voltage, a counting device 8 that counts the number of MHPs included in the output voltage of the filter circuit 11, and an operation that calculates the distance from the measurement object 12 from the number of MHPs It has a location 9, and a display device 10 for displaying the calculation result of the arithmetic unit 9.

  Hereinafter, for ease of explanation, it is assumed that a semiconductor laser 1 of a type that does not have a mode hopping phenomenon (VCSEL type, DFB laser type) is used.

  For example, the laser driver 4 supplies a triangular wave drive current that repeatedly increases and decreases at a constant change rate with respect to time to the semiconductor laser 1 as an injection current. As a result, the semiconductor laser 1 has a first oscillation period in which the oscillation wavelength continuously increases at a constant change rate in proportion to the magnitude of the injection current, and a first oscillation period in which the oscillation wavelength continuously decreases at a constant change rate. It is driven to alternately repeat the two oscillation periods.

  FIG. 2 is a diagram showing the change over time of the oscillation wavelength of the semiconductor laser 1. In FIG. 2, t-1 is the t-1th oscillation period, t is the tth oscillation period, t + 1 is the t + 1th oscillation period, t + 2 is the t + 2nd oscillation period, t + 3 is the t + 3th oscillation period, and t + 4 is The t + 4th oscillation period, λa is the minimum value of the oscillation wavelength in each period, λb is the maximum value of the oscillation wavelength in each period, and T is the period of the triangular wave. In the present embodiment, the maximum value λb of the oscillation wavelength and the minimum value λa of the oscillation wavelength are always constant, and the difference λb−λa is also always constant.

  Laser light emitted from the semiconductor laser 1 is collected by the lens 3 and enters the measurement object 12. The light reflected by the measurement object 12 is collected by the lens 3 and enters the semiconductor laser 1. However, condensing by the lens 3 is not essential. The photodiode 2 converts the light output of the semiconductor laser 1 into a current. The current-voltage conversion amplifier 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

  The filter circuit 11 has a function of extracting a superimposed signal from the modulated wave. 3A is a diagram schematically showing an output voltage waveform of the current-voltage conversion amplifier 5, and FIG. 3B is a diagram schematically showing an output voltage waveform of the filter circuit 11. As shown in FIG. These are obtained by removing the oscillation waveform (carrier wave) of the semiconductor laser 1 of FIG. 2 from the waveform (modulated wave) of FIG. 3A, which is the output of the photodiode 2, and the MHP waveform (superposition) of FIG. (Wave) is extracted.

  The counting device 8 counts the number of MHPs included in the output voltage of the filter circuit 11 for each of the first oscillation periods t-1, t + 1, t + 3 and the second oscillation periods t, t + 2, t + 4. FIG. 4 is a block diagram showing an example of the configuration of the counting device 8. The counting device 8 includes a determination unit 81, an AND operation unit (AND) 82, a counter 83, a rising edge detection unit 84, a falling edge detection unit 85, and a counting result determination unit 86. The current-voltage conversion amplifier 5, the filter circuit 11, the determination unit 81 of the counting device 8, the AND 82, and the counter 83 constitute counting means, and the rising edge detection unit 84, falling edge detection unit 85, and counting result determination unit. 86 constitutes confirmation means for confirming the number of MHPs in decimal units.

  5A to 5D are diagrams for explaining the operation of the counting device 8, and FIG. 5A schematically shows the waveform of the output voltage of the filter circuit 11, that is, the waveform of MHP. 5B is a diagram showing the output of the determination unit 81 corresponding to FIG. 5A, FIG. 5C is a diagram showing the gate signal GS input to the counting device 8, and FIG. These are figures which show the count result of the counter 83 corresponding to FIG.5 (B).

First, the determination unit 81 of the counting device 8 determines whether the output voltage of the filter circuit 11 shown in FIG. 5A is high level (H) or low level (L), as shown in FIG. Output the judgment result.
The AND 82 outputs the logical product operation result of the output of the determination unit 81 and the gate signal GS as shown in FIG. 5C, and the counter 83 counts the rise of the output of the AND 82 (FIG. 5D). . Here, the gate signal GS is a signal that rises at the beginning of the counting period (in the present embodiment, the first oscillation period or the second oscillation period) and falls at the end of the counting period. Therefore, the counter 83 counts the number of rising edges of the output of the AND 82 during the counting period (that is, the number of rising edges of MHP).

On the other hand, the rising edge detector 84 detects the rising edge of the gate signal GS, and the falling edge detector 85 detects the falling edge of the gate signal GS.
The count result determination unit 86 is included in the output voltage of the filter circuit 11 based on the determination result of the determination unit 81, the count result of the counter 83, and the detection results of the rising edge detection unit 84 and the falling edge detection unit 85. Determine the number of MHPs in decimal units. The counting result determination unit 86 determines the number of MHPs according to the counting result determination criteria as shown in Table 1.

  6A to 6I are diagrams for explaining the operation of the counting result determination unit 86. FIG. 6A is a diagram illustrating the gate signal GS, and FIG. 6B and FIG. D), FIG. 6F, and FIG. 6H are diagrams showing examples of output of the determination unit 81, and FIG. 6C, FIG. 6E, FIG. 6G, and FIG. It is a figure which shows the count result of the counter 83 corresponding to FIG.6 (B), FIG.6 (D), FIG.6 (F), and FIG.6 (H).

  First, the counting result determination unit 86 has a determination result of the determination unit 81 when the rising edge detection unit 84 detects the rising edge of the gate signal GS (hereinafter referred to as an initial value of MHP) at a high level and a falling edge. When the edge detection unit 85 detects the falling edge of the gate signal GS, the determination result of the determination unit 81 (hereinafter referred to as the final value of MHP) is also at a high level (FIG. 6B), as shown in Table 1. Thus, the count result of the counter 83 is determined as the number of MHPs without correction.

Similarly, when the initial value of MHP is low and the final value of MHP is also low (FIG. 6D), the counting result determination unit 86 does not correct the counting result of the counter 83 as shown in Table 1. To determine the number of MHPs.
The examples of FIGS. 6B and 6D are examples in which MHPs during the measurement period have ended at a point where the number can be regarded as an integer unit. Since the count result of the counter 83 in FIG. 6C corresponding to FIG. 6B and the count result of the counter 83 in FIG. 6E corresponding to FIG. 6D are both 7, the number of MHPs is also 7 It becomes a piece.

  On the other hand, when the initial value of MHP is at a high level and the final value of MHP is at a low level (FIG. 6F), the counting result determination unit 86 adds 0.5 to the counting result of the counter 83 as shown in Table 1. Is the number of MHPs. Since the count result of the counter 83 in FIG. 6G corresponding to FIG. 6F is 6, the number of MHPs is 6.5.

  In addition, when the initial value of MHP is at a low level and the final value of MHP is at a high level (FIG. 6 (H)), the counting result determination unit 86 calculates 0.5 from the counting result of the counter 83 as shown in Table 1. The value obtained by subtracting is used as the number of MHPs. Since the count result of the counter 83 in FIG. 6 (I) corresponding to FIG. 6 (H) is 7, the number of MHPs is 6.5.

  Thus, the number of MHPs included in the output voltage of the filter circuit 11 can be counted in decimal units. The counting device 8 performs the above-described processing every first oscillation period t-1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4.

  Next, the arithmetic device 9 obtains the distance from the measuring object 12 based on the number of MHPs measured by the counting device 8. The number of MHPs in a certain period is proportional to the measurement distance. Therefore, the relationship between the number of MHPs and the distance in a certain counting period (in this embodiment, the first oscillation period or the second oscillation period) is obtained in advance and registered in a database (not shown) of the arithmetic unit 9. In this case, the arithmetic device 9 can obtain the distance to the measurement object 12 by acquiring the distance value corresponding to the number of MHPs measured by the counting device 8 from the database.

Alternatively, if a mathematical expression indicating the relationship between the number of MHPs and the distance in the counting period is obtained and set in advance, the arithmetic device 9 performs measurement by substituting the number of MHPs measured by the counting device 8 into the mathematical formula. The distance to the object 12 can be calculated. The arithmetic unit 9 performs the above processing every first oscillation period t-1, t + 1, t + 3 and every second oscillation period t, t + 2, t + 4.
The display device 10 displays the distance (displacement) from the measurement object 12 calculated by the arithmetic device 9 in real time. Further, the display device 10 displays the detection / non-detection result of the measurement target 12 based on the measurement target detection signal / non-detection signal.

As described above, in this embodiment, the number of MHPs can be counted in decimal units. Therefore, the distance resolution is improved in a distance meter that measures the number of MHPs using a counter and obtains the distance to the measurement target. Can be made.
In the present embodiment, the counter 83 counts the number of rising edges of MHP, but may count the number of falling edges of MHP. Table 2 shows the count result determination criteria of the count result determination unit 86 in this case.

  When the initial value of MHP is high and the final value of MHP is also high, or when the initial value of MHP is low and the final value of MHP is also low, the same as described above. On the other hand, when the initial value of MHP is at a high level and the final value of MHP is at a low level (FIG. 6F), the counting result determination unit 86 determines 0.5 from the counting result of the counter 83 as shown in Table 2. The value obtained by subtracting is used as the number of MHPs. Further, when the initial value of MHP is low level and the final value of MHP is high level (FIG. 6 (H)), the counting result determination unit 86 adds 0.5 to the counting result of the counter 83 as shown in Table 2. Is the number of MHPs.

  The counting device 8 and the arithmetic device 9 in the present embodiment can be realized by, for example, a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. A program for operating such a computer is provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card. The CPU writes the read program into the storage device, and executes the processing described in this embodiment in accordance with this program.

  The present invention can be applied to a technique for measuring a distance from a measurement object.

It is a block diagram which shows the structure of the distance meter used as embodiment of this invention. It is a figure which shows one example of the time change of the oscillation wavelength of the semiconductor laser in embodiment of this invention. It is a figure which shows typically the output voltage waveform of the current-voltage conversion amplifier in embodiment of this invention, and the output voltage waveform of a filter circuit. It is a block diagram which shows an example of a structure of the counting device in embodiment of this invention. It is a figure for demonstrating operation | movement of the counting apparatus of FIG. It is a figure for demonstrating operation | movement of the count result determination part of the counting device of FIG. It is a figure which shows the compound resonator model of the semiconductor laser in the conventional laser measuring device. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a built-in photodiode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Photodiode, 3 ... Lens, 4 ... Laser driver, 5 ... Current-voltage conversion amplifier, 8 ... Counting device, 9 ... Arithmetic unit, 10 ... Display device, 11 ... Filter circuit, 12 ... Measurement Object: 81 ... Determining unit, 82 ... AND operation unit, 83 ... Counter, 84 ... Rising edge detecting unit, 85 ... Falling edge detecting unit, 86 ... Counting result determining unit.

Claims (9)

A semiconductor laser that emits laser light to the object to be measured;
The semiconductor laser is operated so that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. A laser driver,
A light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal;
Counting means for counting the number of interference waveforms generated by the laser light emitted from the semiconductor laser and the return light from the measurement object included in the output signal of the light receiver;
Determining means for determining the number of interference waveforms in decimal units from the initial value and final value of the interference waveform in the counting period for counting the number of interference waveforms and the counting result of the counting means;
A distance meter comprising: a calculation means for obtaining a distance from the measurement object from the number of interference waveforms determined by the determination means. A semiconductor laser that emits laser light to the object to be measured;
The semiconductor laser is operated so that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. A laser driver,
A light receiver for converting the optical output of the semiconductor laser into an electrical signal;
Counting means for counting the number of interference waveforms generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, included in the output signal of the light receiver,
Determining means for determining the number of interference waveforms in decimal units from the initial value and final value of the interference waveform in the counting period for counting the number of interference waveforms and the counting result of the counting means;
A distance meter comprising: a calculation means for obtaining a distance from the measurement object from the number of interference waveforms determined by the determination means. The distance meter according to claim 1 or 2,
The counting means counts rising edges of the interference waveform,
When the initial value of the interference waveform is at a high level and the final value is also at a high level, or when the initial value of the interference waveform is at a low level and the final value is also at a low level, the determination unit determines the count result of the counting unit. When the initial value of the interference waveform is high level and the final value is low level, the value obtained by adding 0.5 to the counting result of the counting means is determined as the number of interference waveforms. When the initial value of the interference waveform is at a low level and the final value is at a high level, the distance meter determines a value obtained by subtracting 0.5 from the count result of the counting means as the number of the interference waveforms. The distance meter according to claim 1 or 2,
The counting means counts falling edges of the interference waveform,
When the initial value of the interference waveform is at a high level and the final value is also at a high level, or when the initial value of the interference waveform is at a low level and the final value is also at a low level, the determination unit determines the count result of the counting unit. When the initial value of the interference waveform is high level and the final value is low level, the value obtained by subtracting 0.5 from the counting result of the counting means is determined as the number of interference waveforms. When the initial value of the interference waveform is a low level and the final value is a high level, a value obtained by adding 0.5 to the count result of the counting means is determined as the number of the interference waveforms. A wavelength-modulated wave is radiated to a measurement object, interference generated between the wave reflected back to the measurement object and the radiated wave is detected, and a distance from the measurement object is obtained based on the number of interference waveforms. In the distance measurement method,
From the initial value and the final value of the interference waveform and the counting result of the interference waveform in the counting period for counting the number of interference waveforms, a confirmation procedure for determining the number of the interference waveforms in decimal units;
A distance measurement method comprising: a calculation procedure for obtaining a distance from the measurement object from the number of interference waveforms determined by the determination procedure. In a distance measurement method for emitting laser light to a measurement object using a semiconductor laser,
The semiconductor laser is operated so that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. Oscillation procedure
Laser light emitted from the semiconductor laser and return light from the measurement object included in an output signal of a light receiver that converts laser light emitted from the semiconductor laser and return light from the measurement object into an electrical signal A counting procedure for counting the number of interference waveforms caused by
From the initial value and the final value of the interference waveform in the counting period for counting the number of the interference waveforms and the counting result of the counting procedure, a confirmation procedure for determining the number of the interference waveforms in decimal units;
A distance measurement method comprising: a calculation procedure for obtaining a distance from the measurement object from the number of interference waveforms determined by the determination procedure. In a distance measurement method for emitting laser light to a measurement object using a semiconductor laser,
The semiconductor laser is operated so that a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonically and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously exist. Oscillation procedure
The number of interference waveforms generated by the self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object, included in the output signal of the light receiver that converts the optical output of the semiconductor laser into an electrical signal. Counting procedure;
From the initial value and the final value of the interference waveform in the counting period for counting the number of the interference waveforms and the counting result of the counting procedure, a confirmation procedure for determining the number of the interference waveforms in decimal units;
A distance measurement method comprising: a calculation procedure for obtaining a distance from the measurement object from the number of interference waveforms determined by the determination procedure. The distance measuring method according to claim 6 or 7,
The counting procedure counts rising edges of the interference waveform,
In the determination procedure, when the initial value of the interference waveform is high level and the final value is also high level, or when the initial value of the interference waveform is low level and the final value is also low level, the counting result of the counting procedure is When the initial value of the interference waveform is high level and the final value is low level, the value obtained by adding 0.5 to the counting result of the counting procedure is determined as the number of interference waveforms. A distance measurement method characterized in that when the initial value of the interference waveform is at a low level and the final value is at a high level, a value obtained by subtracting 0.5 from the count result of the counting procedure is determined as the number of the interference waveforms. The distance measuring method according to claim 6 or 7,
The counting procedure counts the falling edges of the interference waveform,
In the determination procedure, when the initial value of the interference waveform is high level and the final value is also high level, or when the initial value of the interference waveform is low level and the final value is also low level, the counting result of the counting procedure is When the initial value of the interference waveform is high level and the final value is low level, the value obtained by subtracting 0.5 from the counting result of the counting procedure is determined as the number of interference waveforms. When the initial value of the interference waveform is at a low level and the final value is at a high level, a value obtained by adding 0.5 to the counting result of the counting procedure is determined as the number of interference waveforms.

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